1. Field of the Invention
This invention relates to measuring the coagulation rate of fluids, and more particularly concerns measuring prothrombin time, the time between the injection of a thromboplastin reagent into a sample of blood plasma being tested and the beginning of the formation of the plasma clot.
2. Description of the Prior Art
Prothrombin time indicates the level of prothrombin in a plasma sample and is a measure of the coagulation response of a patient. It is sometimes desired to extend the prothrombin time by having a patient take medicine in an attempt to prevent the formation of blood clots which could cause a coronary artery clot and heart attack or travel through the blood stream to the brain and cause a stroke. One such medicine, coumadin, requires a periodic check of the prothrombin time to make sure the time for starting coagulation is extended, but not extended too far so as to cause internal bleeding.
This invention relates to the inventions disclosed in U.S. Pat. Nos. 3,905,769 ('769) of Sep. 16, 1975 and 5,197,017 ('017) dated Mar. 23, 1993, both issued to Wallace E. Carroll and Richard D. Jackson, and both of which are incorporated herein by reference. The present application discloses an improvement over the methods and apparatus shown and described in both earlier patents.